1. Field of the Invention
This invention relates to a process for preparing .alpha.-naphthol by dehydrogenating ketotetrahydronaphthalene (to be referred to herein for brevity as ".alpha.-Tetralone," a well-known registered trademark), and more specifically, to a process for preparing .alpha.-naphthol which comprises dehydrogenating .alpha.-Tetralone using a catalyst comprising (1) platinum or a platinum compound, (2) an alkali metal salt and (3) a manganese compound and/or a chromium compound supported on a gamma-type alumina carrier.
2. Description of the Prior Art
.alpha.-Naphthol is a very important industrial material useful, for example, as dye intermediates or raw materials for agricultural chemicals.
A number of studies have previously been made on methods for preparing .alpha.-naphthol. Typical prior art techniques are methods such as the alkali fusion of .alpha.-chloronaphthalene and the hydrolysis of .alpha.-naphthalenesulfonic acid. These methods, however, are not free from the formation of .beta.-naphthol as a by-product, and therefore, the resulting product is contaminated with a certain amount of such by-products. Furthermore, these known methods are disadvantageous for commercial mass-production because an undesirable procedure such as alkali fusion is employed. The production of .alpha.-naphthol by the dehydrogenation reaction of .alpha.-Tetralone is described, for example, in U.S. Pat. No. 3,378,591, but the catalyst used in the method disclosed therein has a short lifetime and is disadvantageous as a commercial method.
Lengthy studies on methods for producing .alpha.-naphthol by the dehydrogenation reaction of .alpha.-Tetralone as a starting material in the presence of a catalyst comprising various kinds of metals or compounds thereof supported on alumina have been made to arrive at the present invention.